The present invention relates to firing mechanisms for automatic firearms. In particular, the invention relates to an open bolt firing mechanism for use with programmable ammunition.
Ammunition typically includes a cartridge having a casing and a projectile. Projectiles are often composed of warheads and fuzes. Programmable ammunition receives data instructions that typically relate to the projectile""s mode of operation. These modes of operation often include proximity and variable time modes of function. A proximity fuze initiates a detonation when the projectile reacts to an effect which is produced by a target (e.g. such as infrared radiation from a heat source, sound waves or radar reflection). A time fuze initiates a detonation after a certain flight duration. A variable time fuze may be set prior to firing.
Automatic firearms are designed to be fired repeatedly and continuously. In closed bolt mechanisms, cartridges are repeatedly moved into a firing chamber, where the cartridge is struck by a firing pin. Explosive retained in the casing explodes in the firing chamber causing the projectile to fire. As a result, the temperature of the firing chamber is raised to a point where there is a high risk of a cartridge xe2x80x9ccooking offxe2x80x9d in the chamber prior to being struck by the firing pin.
The risk of cook off has been reduced by the development of open bolt firing mechanisms. An open bolt firing mechanism holds the bolt in a retracted position after automatic firing, thereby preventing a live projectile from remaining in the hot firing chamber. In an open bolt firing mechanism, the projectile is typically fired while the bolt is moving forward toward the barrel. When the projectile is fired, recoil momentum is produced in the bolt. A portion of the recoil momentum is used to stop the forward movement of the bolt, and the remaining recoil momentum is used to return the bolt to its starting position.
Many firing mechanisms, both open and closed bolt, may be used to fire projectiles having electronic fuzes. U.S. Pat. Nos. 6,138,547 and 6,170,377 (incorporated by reference herein in their entirety) disclose cartridges having electronic programmable fuzes. In these shells (i.e., cartridges), programming pulses are transmitted to the fuzes from an external source. The shell may include an electrically conductive band for receiving the programming signals, as disclosed in the aforementioned patents. The programming pulses may be transferred to the band through direct galvanic contact or inductively. In a galvanic system, such as disclosed in U.S. Pat. No. 6,138,547, contact between the external source and the cartridge is made long enough for the programming information to be transferred. In an inductive method, such as disclosed in U.S. Pat. No. 6,170,377, the cartridge is placed in proximity to the external source allowing the programming information to be transferred inductively.
Some programmable cartridges include an energy storage device such as a capacitor that provides an initial supply of electrical power for the projectile to facilitate the transfer of data (programming) prior to set-back of the cartridge. Set-back occurs when the projectile is fired. The force of the projectile rapidly accelerating due to the expansion of gases in a barrel results in high acceleration (or set-back) forces in the projectile. At set-back, the rapid acceleration of the projectile through the barrel provides for the initiation of a continuous power supply during the flight of the projectile. It is desirable to minimize the size of the capacitor, because the size of the capacitor has a large effect on the cost of the cartridge. Capacitor size is related to the complexity of fuze components. One method of reducing the requirement for large capacitor size is to supply the programming information to the projectile late in the firing cycle in order to reduce the required data storage time and power requirements.
Programmable cartridges present special problems for open bolt firing systems. In an open bolt system, during automatic firing the bolt is constantly moving either toward or away from the barrel of the weapon. As the bolt moves forward to chamber the projectile in the barrel, the cartridge normally oscillates. As a result of the movement of the bolt and the associated oscillation, it is difficult to maintain consistent contact or proximity between the external source of the programmed pulses and the conductor located on the cartridge. To date this problem has prevented programmable ammunition from being used effectively with open bolt firing mechanisms. Thus, there is a need for a system or device that maintains the programmable shell or cartridge in a stable position so that programming information can be reliably transferred to the projectile, in order to permit programmable ammunition to be used with open bolt type automatic weapons. The present invention addresses this need and provides other advantages as discussed further below.
It is desirable, from a safety and system operation standpoint, to program the ammunition at the xe2x80x9cpoint of no returnxe2x80x9d. In other words, it is desirable that the ammunition is programmed after the operator pulls the trigger. This insures that the ammunition is programmed with the most recently obtained data. The present invention provides this advantage.
When using inductive setting, it is desirable to maintain close physical proximity between transmission and reception coils. It is also desirable to reduce physical oscillation between separated coils. The present invention provides this advantage. Further benefits of the present invention are discussed below.
According to one embodiment of the present invention, an open bolt firing mechanism for a weapon configured to fire a programmable cartridge is provided. The mechanism includes a firing bolt configured to force the programmable cartridge toward a barrel of the weapon, and a cradle for holding the programmable cartridge adjacent to the bolt. The cradle is configured to carry information for programming the cartridge.
Preferably, the cradle is adapted to move relative to the bolt. More preferably, the mechanism further comprises a biasing mechanism for biasing the bolt toward the barrel. The cradle may include a conductive surface for carrying information to be transferred to the programmable cartridge. Alternatively, the cradle may include a device for generating a magnetic field for transferring information to the programmable cartridge inductively.
According to another embodiment of the present invention, a method of programming a cartridge in a weapon having an open bolt firing mechanism is provided. The method includes the steps of positioning the programmable cartridge adjacent to a firing bolt located in a receiver in the weapon so that the cartridge is between the bolt and a barrel of the weapon, moving the bolt and the cartridge through the receiver toward the barrel of the weapon, and programming the cartridge prior to the cartridge moving away from the bolt.
Preferably, the step of positioning the programmable cartridge adjacent to a firing bolt includes placing the cartridge in a cradle connected to the bolt. More preferably, the step of programming the cartridge includes transferring information from the cradle to the cartridge at a point of contact between the cradle and the cartridge. Alternatively, the step of programming the cartridge includes transferring information to the cartridge inductively.
According to another embodiment of the present invention, a weapon having an open bolt firing mechanism configured to fire a programmable cartridge is provided. The weapon includes a bolt having a bolt face configured to contact the programmable cartridge and force the programmable cartridge toward a barrel of the weapon. A cradle is connected to the bolt for holding the programmable cartridge in a position adjacent to the bolt. The cradle is configured to transfer fusing information to the programmable cartridge prior to the cartridge leaving the bolt face.
Preferably, the weapon further comprises a mechanism for removing a spent casing from the weapon. The geometry of the cradle allows the casing to eject after the cradle extends from its retracted position flush with the bolt face. More preferably, the weapon further comprises a loading mechanism for positioning cartridges in the cradle. In a preferred embodiment, the cradle includes a conductive surface adapted to contact a conductor located on the programmable cartridge so that fusing information may be transferred to the programmable cartridge. Alternatively, the weapon further comprises a device for generating a magnetic field so that the fusing information may be inductively transferred to the programmable cartridge.
According to another embodiment of the present invention, a cradle for holding a programmable cartridge in a position adjacent to a bolt in a weapon having an open bolt firing mechanism is provided The cradle is configured to transfer fusing information to the programmable cartridge prior to the projectile being fired. Preferably, the cradle includes a conductive surface adapted to contact a conductor located on the programmable cartridge so that fusing information may be transferred to the programmable cartridge. Alternatively, the cradle may include a device for generating a magnetic field so that the fusing information may be inductively transferred to the programmable cartridge.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.